1. Field of the Invention
The present invention relates to a milk tank system comprising a first holder configured for intermediate storage of milk from several milkings of a milking device, a second holder for storage of milk from the first holder, a transport device for transporting milk which comprises a milk line from the first holder to the second holder, via which milk line the second holder may be brought into fluidic connection with the first holder, and a shut-off means for shutting off the fluidic connection, in particular from the first holder to the milk line, and wherein the transport device has a first operating state which is configured for collecting milk in the first holder, and a second operating state which is configured for transferring the milk from the first holder to the second holder.
2. Description of Background Art
Such milk tank systems are known, and for example used on large dairy farms. The first holder usually serves as a buffer tank for pumping milk to the milk tank, which is a second holder. In all cases, a milk pump of a standard milking device is rarely sufficiently powerful to overcome the high line resistance of long main milk lines in large dairies without overloading the milk. Also, it is expressly pointed out here that the first holder does not comprise a milk glass such as is normal for many milking devices, including robot milking devices. During milking of successive animals, a milk glass will temporarily store milk from the successive milkings, but it is expressly intended that the first holder can store milk from several milkings simultaneously. The volume will then also be significantly greater than that of an average milk glass, and for example be at least 100 liters. Also, the second holder usually means the milk tank in which milk is cooled and stored until the time of collection by a milk tanker. This milk tank often has a capacity of a few thousand liters, and in each case is many times larger than the first holder.
In practice, the first holder is filled with milk from several milkings and is then emptied into the milk tank. One problem which arises is that the first holder (the buffer tank) is often difficult to clean, in particular in relation to caked milk fat.
It is an object of the present invention to create a milk tank system of the type outlined above in which the abovementioned disadvantage is reduced, and which in particular can be kept clean.
The invention achieves this object with a milk tank system comprising a first holder configured for intermediate storage of milk from several milkings of a milking device, a second holder for storage of milk from the first holder, a transport device for transporting milk which comprises a milk line from the first holder to the second holder, via which milk line the second holder may be brought into fluidic connection with the first holder, and a shut-off means for shutting off the fluidic connection, in particular from the first holder to the milk line, and wherein the transport device has a first operating state which is configured for collecting milk in the first holder, and a second operating state which is configured for transferring the milk from the first holder to the second holder, wherein the milk tank system furthermore has a control system for switching the transport device from the first to the second operating state when the milk in the first holder reaches a temporally changeable switching milk level.
The concept behind the present invention is that pumping of the milk out of the first holder does not always begin at the same milk level in the holder. However a layer of foam or milk fat, milk protein or similar always forms on the milk, residue from which may remain behind when the first holder is pumped out. If, as in the prior art, pumping always takes place at the same level, then an ever thicker and further hardening layer of milk fat will be deposited on the wall of the first holder at this level. By starting the pumping out at a level which changes over time, as in accordance with the present invention, this caking and hardening of the milk fat will take place to a far lesser extent. Subsequent cleaning of the first holder can then be carried out more easily and/or better.
It is pointed out here that a switching milk level changeable over time means that the milk level at which switching between the two operating states takes place varies over time. Finally, the milk level itself will also vary over time on supply or discharge of milk, but the relevant factor for the invention is the switching milk level at which the operating state is switched.
The transport of milk by the transport device here means either active or passive transport of milk. The latter includes transport under the influence of gravity, such as in pipes on a gradient and similar. Active milk transport comprises transport by means of a pump or similar. Combinations of the two transport types are also possible.
The first operating state of the transport device here means that milk is captured and collected in the first holder without being able to flow to the second holder, and the second operating state means the state in which the milk can flow from the first holder to the second holder, again actively and/or passively.
It is also pointed out here that the advantage of the present invention is particularly evident on use of this system in a milking system with automatic milking devices and free traffic of animals. The moment of milking the animals is not fixed, and is arbitrarily spread over the day. Thus, much more than with scheduled milking events two or three times a day, it is possible that for some time no milk may be transferred to the first holder. In such a case in particular, caking of the milk fat on the wall of the first holder may take place. This can be a problem in particular if, just before a fixed switching milking level, no fresh milk is added for some time and then so much new milk is added at once that pumping begins. The caked milk fat will then scarcely have time to be dissolved by new milk.
Particular embodiments of the invention are described in the dependent claims and in the description below.
In certain embodiments, the switching milk level is non-decreasing during a time interval, and has a different value for at least two time points during the time interval. In these embodiments, the time interval is selected such that the first holders are emptied at least twice on average. The selection of the time interval may be based on historic averages or similar. Also, in practice, the first holder is usually emptied more often than twice before it is cleaned, but this depends on the size of the dairy and the number of connected milking devices and similar. In said embodiments therefore, emptying of the first holder begins at a higher level each time. Therefore any caked milk residue from most “filling events” will be rinsed away at least partly on subsequent filling of the first holder.
In particular, the switching milk level is strictly increasing at least during a time interval. In these embodiments, on a subsequent emptying of the first holder, the switching milk level is in each case higher than the present level. This ensures optimum rinsing of the milk fat rim, and hence as little caking of milk fat and similar as possible.
In certain embodiments, the switching milk level changes arbitrarily at least during a time interval. In such embodiments, because of statistical variation, the wall of the first holder will be loaded with the milk (fat) deposits as evenly as possible, so that thick deposits occur as little as possible.
In certain embodiments, the switching milk level varies within a predefined bandwidth around the base value, and the base value has an increasing value during the time interval. In these embodiments, the switching milk level will gradually rise, but temporarily may vary within a relatively limited margin. These embodiments also are intended to minimize the local deposit load.
In certain embodiments, the time interval has a predefined and in particular fixed value, and the switching milk level after expiry of the time interval is lower than a switching milk level during the time interval, and in particular equal to a lowest switching milk level during the time interval. Here it is always possible that the switching milk level varies, in particular increases, during the time interval but after expiry of the time interval the switching milk level For these embodiments, a regime is applied so that the switching milk level may be reset. The switching milk level may not continue to rise unlimitedly. In particular, a cleaning interval time is set for the time interval. This is often set to eight hours, so that the first holder is cleaned three times per day. Also however other times are possible, such as for example on the basis of legal stipulations. Another example is a time period of for example two hours, within which period the milk obtained must be cooled to a lower temperature such as 4° C. If for example the first holder is then not yet filled to the switching milk level originally set, the system still switches from the first to the second operating state in order to empty the first holder. In all cases, after emptying, a different switching milk level may be set, wherein if the first holder is cleaned, the switching milk level is reset to the lowest base value, whereas after simply emptying the first holder, the switching milk level may be varied following previously set criteria, as discussed above.